Generally, in semiconductor elements such as semiconductor laser elements and high-frequency elements that are used in optical communications and the like, the problem of how to efficiently remove the heat generated by said elements is very important for preventing malfunctions and the like. In recent years, advances in semiconductor element technologies have resulted in elements with higher outputs, higher speeds and higher integration, placing even stricter demands on the heat dissipation thereof. For this reason, higher thermal conductivity is also generally required in heat dissipation components such as heat sinks, and copper (Cu), which has a high thermal conductivity of 390 W/mK, is used.
Meanwhile, individual semiconductor elements are becoming larger in size with the higher outputs, and the problem of mismatches in the thermal expansion between semiconductor elements and the heat sinks used for heat dissipation has become more prominent. In order to solve these problems, the development of a heat sink material that has the property of high thermal conductivity while also having a coefficient of thermal expansion that matches that of semiconductor elements has been sought. As such materials, composites of metals and ceramics, for example, composites of aluminum (Al) and silicon carbide (SiC), have been proposed (Patent Document 1).
However, the thermal conductivity of an Al—SiC composite will be 300 W/mK or less no matter how the conditions are optimized. Thus, the development of a heat sink material having even higher thermal conductivity, equal to or greater than the thermal conductivity of copper, has been sought. As such a material, a metal-diamond composite combining the high thermal conductivity possessed by diamonds with the high coefficient of linear expansion possessed by metals, and thus having high thermal conductivity and a coefficient of linear expansion close to that of semiconductor element materials, has been proposed (Patent Document 2).
Additionally, in a heat dissipation component for use in a semiconductor element, it is necessary to add a metal layer, by plating or the like, to the surface of the heat dissipation component in order to join it to the element. In the case of a normal semiconductor element, the heat dissipation component is primarily joined by soldering and the joining temperature is 300° C. or lower, so a metal layer is provided by plating an Ni—P alloy or the like on the surface. However, with the higher outputs of semiconductor elements, there are cases in which a semiconductor element and a heat sink material are arranged to be in contact by being joined by using a brazing material or the like in order to efficiently dissipate the heat generated by the semiconductor element. In such applications, due to the elevated joining temperatures and the increase in the temperature load at the time of actual use, when conventional alloy plating such as Ni—P alloy plating is used, the difference in the linear expansion between the heat sink material and the plating film causes blisters to form. For this reason, multilayered plating with Ni layers and amorphous Ni alloy layers has been proposed (Patent Document 3).